The present invention relates to hangers for conveyors, for example, for use in coating lines for motor vehicle bodies.
In conventional coating lines comprising an overhead trolley conveyor for the electrodeposition coating of motor vehicle bodies, the vehicle body while being transported is guided into the bath of an electrodeposition tank so as to obliquely plunge thereinto and is obliquely withdrawn from the bath. This prevents the vehicle body from floating up with smooth discharge of air from inside the body when it is immersed into the bath, and further permits the electrodeposition bath to smoothly flow out from inside the body when it is withdrawn from the bath. In this case, it is practice to determine by experiments the optimum angle at which the vehicle body is to be plunged into the electrodeposition bath and the optimum angle at which the vehicle body is to be withdrawn from the bath.
The carrier of the conventional trolley conveyor has a hanger which comprises an upper frame suspended from a free trolley, a lower frame for loading thereon the vehicle body to be transported, and a pair of front and rear arms interconnecting the upper and lower frames. However, since the front and rear two arms extend vertically in parallel to each other, there is a need to give a large angle of inclination to the free rail at the location where the vehicle body is to be obliquely plunged into the electrodeposition bath. Otherwise, the vehicle body can not be guided into and withdrawn from the bath at a predetermined large angle. Thus, it is not easy to design the conveyor line.
To overcome this problem, we have conducted continued research and proposed a hanger rocking device having side rollers and provided on the carrier, and a guide rail disposed below the free rail and having a large angle of inclination at the location where the vehicle body is plunged into or withdrawn from the electrodeposition bath to cause the inclined portion of the guide rail to guide the side rollers of the hanger rocking device and obtain a large angle at which the vehicle body is to be plunged into or withdrawn from the bath (see, for example, Unexamined Japanese Utility Model Publication HEI 3-69567). However, the proposal has the problem of an increased equipment cost because of the necessity of providing the roller-equipped rocking device on the carrier and installing the guide rail in combination with the free rail for guiding the side rollers.